JEEP GRAND CHEROKEE RADIO PROBLEM

1995 Jeep Grand Cherokee • 202,000 miles

I am getting no sound out of my factory Chrysler Infinity Gold cassette stereo system. The HU illuminates and is receiving power from both the 12V constant and switched circuits. I have a remote amplifier under the driver side rear seat and it too is receiving power. I have checked continuity of the wires leading to the amp and they are intact.

The speakers appear to be capable of functioning as I have hooked a power source to them and have heard the "pop" associated with functionality. I have checked continuity of the leads of the speakers and the connections and they appear intact.

I have checked the fuse : (#10 I believe) which is specific to the radio and it was fine. I swapped out the amplifier with one from the junkyard and the problem persists.

Please note that the power antenna has been snapped off and I cannot determine if the motor is operable or not. I can tell you that no sound is audible from the motor.

Besides the 12 volt feed and ground wires to the amp, it has to receive the turn-on signal from the radio. That's the same wire that feeds the power antenna. With the radio still plugged in, use a jumper wire to connect either power wire to the turn-on wire. If the amp turns on, there is either a relay in the radio that has bad connections or a transistor circuit that has a problem, depending on the model number. The wires to connect are the one farthest away from the key way in the end of the black plug, to one of the two farthest away from the key way in the gray plug. I prefer using the second wire from the end since that's the main power wire and is on a larger fuse. (That's "Acc" to "Ant).

If that works, it might be less expensive to find a used radio in a salvage yard, but sooner or later they all develop the same problem. Once repaired, they're fixed for life because we use beefier parts. The radios for '93 - '95 Jeeps have different mounting ears than most other Chrysler radios. Those ears were also used in the late '90s Avenger but they had orange displays. Also, look for another Infinity radio. All Chrysler radios put out speaker-level output and will run the speakers directly without an amplifier. The Infinity radios put out much less bass, then it is made up in the amplifier for the shape of the vehicle. If you use a standard radio, you'll have too much bass unless you turn it way down.

I have tried the same suggestions you provided. When jumping either of the two power wires with the last connection on the black connector, no change occurs.

Please note that I have changed the problem radio with another stock radio from the junk yard and the issue remains.

I am thinking that it's a ground issue and that the inoperable antenna figures into this somehow. I removed the old radio and attempted to operate it externally. I hooked up my charger to the two power pins in the back and used alligator clips to the 1st and 5th pins to hook up a speaker I had laying around to see if it would play. Although no antenna was hooked up to it, I thought I would hear some type of static at the very least. Alas, no sound was forthcoming.

Any other suggestions or directions to provide me? I'm pretty good at following instructions.

Please note that no sound emanates from the speakers no matter which band nor function I attempt to use i.E. FM/AM or tape. Either there's a ground issue or the amp is not turning on. It might be because of a broken ground since I don't have power to the rear windows nor my horn or some other fuse related matter. I have checked Fuse #s 1, 4, 8, 10 and 24 and they all appear to be intact although I have not put a continuity test to them.

I haven't done that yet, but I don't anticipate anything different. The model number of both radios is the same - 4704315. Would a broken wire in the driver side door cause any of this issue? If it were a ground wire?

No to both. The only wires between the door hinges are two for each speaker. If there's separate dash speakers, the left one would still work even if there was a broken wire to the door speaker.

There's no ground wire in the two connectors. The antenna shield, (the outer braided shield in the wire), will provide a ground but it's not a good one. There will be a flat braided ground strap or a black wire bolted to the back of the radio, or a black wire clipped to a stamped terminal on the back of the housing. If the ground was missing, the radio would be dead, including the display.

Lets go back to the basics. Measure the voltage on the "Ant" wire. There should be 12 volts there when the ignition switch and radio are turned on. If there is, find that same color wire at the amp and check for the same voltage there.

Ok, so it appears the both of the radios are bad. I jumped the power and the remote connections and the left side speaker and the front tweeters came alive. I then tried it on the salvage radio and the same situation.

Now this solves the great mystery, but I need to know my options. What would it cost to repair the radios at your shop or is it something I can accomplish with my limited soldering skills?

Additionally, I am concerned about the poor sound quality from the other speakers. As I moved the balance control to isolate the rear speakers, no sound could be heard emanating from the rear speakers and only faintly from the passenger front speaker. The tweeters in the front dash did not appear to be fully operational either. Is this a product of the radio issue i.E. Some of the channels going bad?

Well, the good news is there is no relay or turn-on circuitry in your radio. The switched 12 volts at the power antenna terminal comes straight off the power switch. I've repaired hundreds of arced switches years ago, but never one on your model. I'd find it odd for two of them to be causing a problem, let alone one.

There is a fuse resistor at the end of the 12 volt line after that supply has fed the output I.C.S and the other circuitry. My suspicion is something is shorted on the turn-on circuit in or to the amp and it burned that fuse resistor open. That would do the same thing to the replacement radio, which would explain why they both have the same problem.

Do these tests in the diagram below. Measure the continuity between the switched ignition wire and terminal 5 in the round cd changer socket. Don't ask me how they came up with that numbering but I drew the picture with pretty red and black meter leads to avoid confusion. You should find 0 ohms with the power switch turned on, plus the small normal resistance in the meter leads. This part of the circuit should be good, otherwise the radio wouldn't play at all.

Next, measure from pin 5 to the power antenna terminal as shown with the nifty blue meter lead. You should read 1.2 ohms plus the meter lead resistance. If it reads open, that fuse resistor is burned open. If that's the case, go to the black plug in the vehicle and read the resistance between that wire and ground. It should read very high or open. If it reads a relatively low value, read it again after you unplug the connector from the amplifier. If it still reads low, that wire has rubbed through the insulation and is shorted to the body. Gotta fix that. If it reads open now, something in the amp is shorted.

I don't have service manuals for most of the amplifiers but there's a good chance I can figure out the problem and fix it. It would be easier though to try to find another one in a salvage yard. If you're anywhere between Ohio and southern Georgia, there is a real nice chain of yards called "Pull-A-Part" where you pay your buck, throw your tool box in one of their wheel barrows, and you can spend all day there. I bought a lot of Chrysler amps from them including one to replace mine in my '93 Dynasty with only 4,200 miles. The turn-on circuitry failed on it too, I suspect from constantly disconnecting and reconnecting the battery. Those amps only cost me 18 bucks each. Finding one for my Dynasty was real hard because only about one car in a hundred came with the premium sound system. The Infinity system in your Jeep was real common so amps should be easy to find.

First of all, thank you for all your help. I assumed we had found the problem and it was two defective radios - what's the odds of that. Now, it appears what I always suspected - a short some where.

I am clear on all your instructions except as to how you want me to check the black wire. I assume you mean to check the ground wire connected separately to the large bolt on the back of the radio. I also assume that you want me to test continuity by touching one of the multimeter leads to that wire once disconnected from the back of the radio and the other lead to some known ground point i.E. The negative battery cable or seat bolt. If this is correct, please advise and I will do so straight away.

Please note that I have installed a salvage amp in place of the original amp as I thought it might be the problem as well. As such, I would find it quite odds-defying if both of the amps were defective - the same odds-defying chance that both radios had the same defect.

If there was a short some where, wouldn't the fuse blow or some noise indicative of this be heard upon connecting the radio or amp?